Cng Research Company

Controlsoft, Inc.

Coleman B Brosilow

Robert J Adler

William R Brown

Nelson C Gardner

A method of controlling a process including at least two process variables and at least two control efforts, with each control effort having an influence on at least one process variable, including the steps of modelling the influence that a change in each control effort has on each process variable; describing the desired trajectory which each process variable will follow towards its desired value in response to a system change; and, coupling the control of each process variable; whereby changing a first set of at least one control efforts so as to cause a desired change in at least one process variable can be compensated for by a change in a second set of at least one control efforts so that substantially no influence in exhibited on other process variables in the system in which no change is desired. The method may include delaying a desired change in such first set of control efforts a time equal to the maximum dead time lapse of any control effort of such second set of control efforts relative to any such process variable for which no change in desired.

Modular multivariable control apparatus and method

A process for separating acid gases such as CO.sub.2, H.sub.2 S, and SO.sub.2, other sulfur-containing molecules such as COS, and other relatively high boiling point impurities from lower boiling point components of a gas stream comprises: dehydrating the gas stream and contacting it, at an elevated pressure and at substantially the dew point temperature of carbon dioxide therein, with a liquid carbon dioxide refrigerant-absorbent to absorb such impurities other than CO.sub.2, and separating the liquid carbon dioxide and absorbed impurities; condensing CO.sub.2, and separating the liquid carbon dioxide and absorbed impurities; and condensing CO.sub.2 from the residual gas stream at such pressure, preferably by indirect heat exchange. A crystallization process is also disclosed for separating the liquid carbon dioxide and absorbed impurities. The residual gas stream obtained following indirect heat exchange may be processed further by contact with a second refrigerant-absorbent which preferably comprises a liquid-solid slurry. Further, a crystallization process is disclosed for separating a crystallizable material and an excluded material which is at least partially excluded from the solid phase of the crystallizable material obtained upon freezing a liquid mixture of the materials. The solid phase is formed and melted at spaced locations in a liquid mixture of the materials and, within the liquid mixture, internal solid and liquid flows are maintained in opposite directions to effect separation of the materials. The solid phase is formed by evaporative cooling of the liquid mixture and melted by direct contact with a condensing vapor phase of the materials, each of these operations being performed substantially at the prevailing triple point locus conditions in the respective locations in the liquid mixture.

Gas separation process

A crystallization process is disclosed for separating a crystallizable material and an excluded material which is at least partially excluded from the solid phase obtained upon freezing a liquid mixture of the materials. The solid phase is formed and melted at spaced locations in a liquid mixture of the materials and, within the liquid mixture, internal solid and liquid flows are maintained in opposite directions to effect separation of the materials. The solid phase is formed by evaporative cooling of the liquid mixture and melted by direct contact with a condensing vapor phase of the materials, each of these operations being performed substantially at the prevailing triple point locus conditions in the respective locations in the liquid mixture.

A process for separating acid gases such as CO.sub.2, H.sub.2 S, and SO.sub.2, other sulfur-containing molecules such as COS, and other relatively high boiling point impurities from lower boiling point components of a gas stream comprises: dehydrating the gas stream and contacting it, at an elevated pressure and at substantially the dew point temperature of carbon dioxide therein, with a liquid carbon dioxide refrigerant-absorbent to absorb such impurities other than CO.sub.2, and separating the liquid carbon dioxide and absorbed impurities; condensing CO.sub.2, and separating the liquid carbon dioxide and absorbed impurities; condensing CO.sub.2 from the residual gas stream at such pressure, preferably by indirect heat exchange; contacting the residual gas stream at such pressure with a second refrigerant-absorbent below the triple point temperature of carbon dioxide, and separating additional carbon dioxide therewith. The second refrigerant-absorbent is preferably a liquid-solid slurry comprising an organic liquid vehicle and carbon dioxide in the solid phase to provide in situ refrigeration by melting of the solid phase. The final, residual gas stream is heat exchanged to recover its refrigeration potential. Further, a crystallization process is disclosed for separating a crystallizable material and an excluded material which is at least partially excluded from the solid phase of the crystallizable material obtained upon freezing a liquid mixture of the materials. The solid phase is formed and melted at spaced locations in a liquid mixture of the materials and, within the liquid mixture, internal solid and liquid flows are maintained in opposite directions to effect separation of the materials. The solid phase is formed by evaporative cooling of the liquid mixture and melted by direct contact with a condensing vapor phase of the materials, each of these operations being performed substantially at the prevailing triple point locus conditions in the respective locations in the liquid mixture.

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Cleveland Heights, OH, United States of America

Coleman B Brosilow